Samarium chemisorption on group-IV semiconductors

Abstract

Samarium is an excellent test system with which to study the interaction between chemisorbed metallic overlayers and different kinds of substrates because the $4f$ configuration is sensitive to the Sm valence state. We used this unique feature to study the chemisorption of Sm on cleaved Ge(111) and Si(111) surfaces. In both cases, synchrotron radiation photoemission spectra exhibited only divalent Sm features at coverages below 2-3 Å and a mixture of trivalent and divalent Sm features at higher coverages. This transition was accompanied by strong adatom-substrate chemical interactions as revealed by large core-level shifts.